Materials Science at IgMin Research | Engineering Group

An experimental investigation was carried out to study the effect of circular cross-holes on the failure behavior of unidirectional glass fiber reinforced with unsaturated polyester resin composites, varying cross-ply laminates that were subjected to axial tensile load. This paper deals with the effects of the circular notch and the number of plies on nominal tensile and net tensile strengths. Tensile strengths were investigated for composites with cross-ply([0/90]. [90°/0°/90°] and [0°/90°/0°].90°), orientation and ...varying the laminate layers with a central hole, and effects of volume fraction and number of ply on mechanical properties for un-notched (smooth) and notched specimens were also studied. The results showed that increasing the number of plies has a marginal effect on tensile strength values. The fraction of volume has significant effects and for increasing the number of plies about 9% decreases in nominal tensile strength and about 11% decrease in the net tensile strength was observed. The same results were obtained with finite element analysis.Read more

The experimental team has developed a technology of step-by-step low-temperature diffusion doping of gadolinium and scandium into silicon that allows the clusters of impurity atoms to be uniformly distributed throughout the entire bulk of the silicon material. It was shown that, unlike the samples obtained under the high-temperature diffusion doping technology, in the samples obtained under the novel technology the team had detected any surface erosion or formation of alloys and silicide in the near-surface region. The authors have revealed inc...reased thermostability and radiation resistance of silicon samples dotted with clusters of impurity atoms of gadolinium and scandium.The authors have conducted comprehensive studies by using the techniques of tagged atoms, autoradiography, measurement of conductivity and Hall effect, isothermal relaxation of capacitance and current of diffusion, solubility, and electrophysical properties of scandium in silicon under various doping conditions and for a wide temperature range (1100 ÷ 1250 0С). Diffusion parameters, solubility and acceptor nature of scandium in silicon as well as thermal stability of silicon doped with gadolinium and scandium impurity atoms have been established.Read more

In materials science, the integrity and completeness of datasets are critical for robust predictive modeling. Unfortunately, material datasets frequently contain missing values due to factors such as measurement errors, data non-availability, or experimental limitations, which can significantly undermine the accuracy of property predictions. To tackle this challenge, we introduce an optimized K-Nearest Neighbors (KNN) imputation method, augmented with Deep Neural Network (DNN) modeling, to enhance the accuracy of predicting material properties.... Our study compares the performance of our Enhanced KNN method against traditional imputation techniques—mean imputation and Multiple Imputation by Chained Equations (MICE). The results indicate that our Enhanced KNN method achieves a superior R² score of 0.973, which represents a significant improvement of 0.227 over Mean imputation, 0.141 over MICE, and 0.044 over KNN imputation. This enhancement not only boosts the data integrity but also preserves the statistical characteristics essential for reliable predictions in materials science.Read more

This work represents a part of a larger work, aimed at evaluating the fouling behavior of different flat polymeric membranes for low-pressure applications when placed in contact with industrial wastewater (IWW). To design and understand the operation of a membrane process it is essential to know the fouling mechanisms.Commercial PVDF and PS membranes were tested under static conditions. The reduction in membrane flux was calculated, before and after the fouling tests. Parameters such as membrane material, pore size, solids concentration, partic...le size, pH, temperature, flow rate, and pressure were studied to identify the fouling behavior of the membrane.The strong adhesion of organic molecules on the membrane surface develops a resistance to pore blockage which allows a significant decrease in the flow of clean water.It is important to note that membranes of the same material, PVDF, but with different pore size (0.2 and 0.5 mm), and membranes of different materials, PVDF and PS, but with the same pore size (0.2 mm) were tested to study the trend of surface fouling to predict it and/or design surface modifications of the membranes employed.A morphological analysis of the membranes was carried out to understand the fouling mechanism, the fouling times, and the nature of the block that determines the reduction of flow through the membrane itself.Roughness measurements reveal that roughness goes up to 120 minutes of immersing time in wastewater, but after 4 hours it returns to initial value but with a significant decrease of flux to water.Understanding the relationship between flux decline, morphology, and roughness role is key to preventing fouling and studying a valid method to clean the membrane.Read more

The paper explores comprehensive Unmanned Aerial Vehicle (UAV) wing optimization, integrating aerodynamic and structural techniques. A detailed comparison between the base and optimized modules while considering specifications such as composite material orientation, spar and rib material, deformation, stress, strain, safety factor, and weight. The methodology utilizes material changes for wing weight reduction while maintaining structural integrity. The optimized module (Case 7) balances weight reduction, safety, and structural performance, not...ably shifting from Al 7075 to Al 2024. Structural optimization focuses on changes in Carbon Fiber/Epoxy orientation, leveraging material changes for weight reduction. Constitutive equations and transformation matrices calculate stiffness matrices for the laminate, resulting in a robust wing. This holistic optimization combines low and high-fidelity techniques, addressing UAV wing structural aspects. Outcomes include weight reduction, deformation minimization, fluttering modal deformation and buckling points, an increased factor of safety, and improved strength-to-weight ratio. The research significantly advances aerospace engineering, particularly in UAV design and optimization.Read more

Fractals are complex structures that repeat themselves at several scales. Nature exhibits these in many forms like snowflakes, mountains, coastlines, the human brain/lungs/ nervous system, and many more. It appears that these are nature’s organic way of growth. Thus, there is an underlying science that works to grow or create these self-similar patterns. In this work, tin oxide-based fractals have been grown under laboratory conditions and applied to a gas-sensing field. The facile growth methodology successfully grows fractals on a large... scale. The tin oxide fractals have unique basic building units that connect and grow in different directions. These tin oxide fractals have successfully sensed ethanol vapors in the range of 20 ppm to 100 ppm. The best sensing response has also detected ethanol vapors as low as 10 ppm at room temperature with response and recovery times of 18 ± 3 s and 22 ± 5 s, respectively. The best sensing response recorded for such sensors was under 12 s. The characteristic fractal growth is attributed as the defining factor that enhances ethanol sensing at room temperature.Read more

The use of polycarboxylate ether superplasticizer PCE in the preparation of mortars and concretes influences the hydration kinetics and the amount of total heat released. This leads to a modification of certain properties of the mortar, namely workability, calorimetry and mechanical resistance. In this study two ether polycarboxylate superplasticizers with different chemical structures were used; they were incorporated at different dosages into a standardized cement-based mortar. The objective of this work is to study the effectiveness of these... superplasticizers and to select the most compatible product with cement and the most suitable for use according to the climates of the country. The impact of superplasticizers on fresh cement was studied by measuring the Marsh cone flow time and calorimetric measurement. In the hardened state, the mechanical properties were provided by measuring the compressive strength. The results show that low dosages of ether polycarboxylate superplasticizer promote grain hydration and produce more heat. On the other hand, high dosages delay the contact of the cement grains with the mixing water and cause a reduction in the final heat released and a delay in setting. The ether polycarboxylate superplasticizer with high carboxylic density gives the best mechanical resistance compressive at 7 and 28 days.Read more

The textile sector has great relevance in the Brazilian socioeconomic context, generating large volumes of effluents of varied composition, with dyes being one of the most worrying contaminants due to their characteristics of high solubility, harmfulness and low degradability. Among them the Reafix Yellow B8G (ARB8G) dye has an azo nature, harmful to organisms in the aquatic environment. According to Brazilian laws, it is recommended to dispose of waste through incineration or landfill, due to its resistance to biodegradation. One of the method...s for treating effluents is the adsorption of contaminants using materials with adsorption capacity, such as residue from the burning of biomass in boilers (ash). The general objective of this work was to evaluate the adsorption kinetics by contact time of the ARB8G dye by boiler ash. The test was based on mixing the adsorbent material with a dye solution at 75 mg.L-1, at constant temperature and stirring at different time intervals. To quantify the amount of adsorbed dye, the UV-Vis spectrometry method was used. The kinetic test indicated an equilibrium time of 30 minutes, with 100% removal under the tested conditions. From this result and considering that boiler residue is an underutilized and low-cost material, it is concluded that this substance has significant potential to be applied as an alternative material for the treatment of effluents containing dyes.Read more

A new design of a fine positioner or high precision driven unit with a large positioning range is proposed for a custom-made in-situ indenter device equipped inside an SEM chamber. The design configuration of the proposed system is size-effective for the confined working area of the SEM chamber. The indentation depths can be precisely varied by controlling the fine positioner driven by a piezoelectric actuator. The main goal is to achieve very deep penetrations toward the bottom layers of tall or large-size scale specimens by single indentation..., without the need for sequential indentations. Thus, the proposed design can eliminate the need for sequential adjustments of the specimen position with respect to the indenter tip as currently being practiced by the researchers. The specimen position adjustment after each indentation heavily depends on the coarse positioner and its accuracy level in a sub-millimeter regime which could result in position errors and unwanted lateral forces in the nanoindentation process. Therefore, the sequential indentations technique could lead to considerable variations in the outcomes of nanoindentation tests done on similar specimens. The proposed design will be realized to deploy in the Continuous Stiffness Measurement (CSM) techniques generally used to evaluate elastic properties as a function of continuous penetration depth with high-frequency loading and unloading cycles.Read more